RequiredIfOtherFieldsNotGiven - was documented but not implemented.
RequiredIfOtherFieldsGiven - was implemented but not documented.
RequiredIfOtherFieldGiven - was implemented but not documented.

Broke the compound conditions in the validators into separate if statements, because trying to figure out what anded nots in a loop were supposed to do was making my brain hurt.

Provided some doctests for these validators. (uploaded separately)

Finally, the documented behaviour of RequiredIfOtherFieldsNotGiven was a little odd. Whereas the validator used to require a value if any of the other fields was not given, it now requires a value only when none of the other fields is given. Since the validator was not implemented previously, this is not a breaking change.

The validator framework is deprecated functionality at this point, so we aren't adding any more features to it. What I've done is removed the documentation for the non-existed RequiredIfOtherFieldsNotGiven and merged in alang's documentation for RequiredIfOtherField[s]Given.